Datamodel: don't generate async VDI.get_nbd_info
Datamodel: don't generate async VDI.get_nbd_info

There is no need for this, as it shouldn't be blocking. Each host has to
read a file to get their certificates, but it still shouldn't take long.
And we can always re-add it in the future.

Signed-off-by: Gabor Igloi <7535f5501fd71876c93d896691e178fd3a11cfbb@citrix.com>

srowe/xen-api,srowe/xen-api,srowe/xen-api,srowe/xen-api,srowe/xen-api